Lease renewal with second tenant moving in?

[Miguel Berberena]

Super simple for anyone but me....I have a rental and lease is up for renewal.  Tenant asked to move her fiance in which I approved.  1- Should I have them sign a new lease or should I do a renewal and add him to it?   2- should I add a clause that she is the primary since he would not be approved to live there on his own due to his income or does that not matter.  I want to avoid the break up and she moves out and he stays and can't really afford the apartment?  Thanks for the help